I want to make non-blocking loop over array with objects, so I used async.each function:
log.info("before");
async.each(products , function(prdt, callback){
for(var i = 0 ; i <4000000000; i++){
var s = i;
}
console.log("inside");
callback();
}, function (err) {
console.log("end");
});
log.info("after");
So if I run code above I have a such messages output:
before
inside
....
inside
end
after
If async.each asynchoronous why I dont see output in that order?
before
after
inside
inside..
end
UPDATE1: thx for answers, but If I want to execute that code inside my router, I will blocked all responces to my server? What I need to change?
Seems to me that the async.each
function is simply implying that it can be used for asynchronous actions because it inherently includes a callback function (which is trivial for you to add yourself in your own function).
Consider this code which uses Mongoose (a MongoDB wrapper) to simulate a real-world asynchronous call:
console.log("before");
async.each(["red", "green", "blue"], function(color, cb) {
mongoose.model('products')
.find({color: color})
.exec(function(err, products) {
if (err) return cb(err); // will call our cb() function with an error.
console.log("inside");
cb(null, products);
});
}, function(err, products) {
if (err) return console.error(err);
console.log("really after");
console.log(products);
});
console.log("after");
You'll get
before
after
inside
really after
[red products]
inside
really after
[green products]
inside
really after
[blue products]
Does it make sense why? Let me know if I can break any of this down further.
async.each() is asynchronous, but you're not doing anything that is blocking or requires an asynchronous loop. If you put a setTimeout() in there you'd see it working like you expect.
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